Measurement of the Propulsion Dynamics of Light-Activated Janus Particles via Optical Microscopy and Optical Tweezers
In the field of active matter, there has been a great interest in developing self-propelled micromotors that can mimic biological motion. Light-powered micromotors are a type of active Janus particles that convert chemical energy into motion by mechanisms that depend on the input of light. However, the magnitude of the propulsion force generated by these particles has not been directly measured. In this work, we fabricated light-activated AuTiO2 Janus particles and observed that large-size particles exhibit higher propulsion velocity and more directional trajectories under UV irradiation compared to green light. To directly measure the propulsion forces, we synthesized core-shell particles composed of polystyrene cores and TiO2 shells that are stably trapped in the optical tweezers. We observed transient propulsion events in H2O2 under UV or green laser with forces up to 20 pN. Our study presents a novel approach to measuring the force and velocity produced by these powered micromotors.
Katherinne received her B.S. in Chemistry from PUCP and Ph.D. in Chemistry from Rice University. She was advised by Prof. Eugene Zubarev in colloidal synthesis, characterization, and functionalization of nanomaterials for biomedical applications. Her recent postdoctoral training as a joint postdoc in the Alivisatos and Bustamante lab at UC Berkeley studying active colloids allowed her to gain experience to develop nanofabrication skills using state-of-the-art equipment at the Molecular Foundry (Berkeley Lab). Currently, as part of the Bustamante research group, she is using novel optical probes and nanofabricated devices to perform single-molecule biophysics experiments.
High Coherence 2D Kerr-Cat Qubit: Experimental Realization and Technical Challenges
The Kerr-cat qubit is a bosonic qubit in which the information is encoded in multi-photon cat states. The suppressed bit flip rate makes this qubit a promising candidate to implement quantum error correction codes tailored for noise-biased qubits. Moreover, its intrinsic nonlinearities enable fast logic gates and QND measurement. However, the strong two-photon pump drive, which stabilizes the cat-state, introduces both theoretical and practical challenges when large cat sizes or multi-qubit operations are desired. Here, we present an experimental realization of high-coherence Kerr-cat qubits in a 2D superconducting circuit. With a novel on-chip filter significantly increasing the qubit-pump coupling, we can generate large cats with smaller drive power and explore the bit-flip dependence on the cat size. With bit-flip times approaching 800us for a cat of size 8 photon, our work paves the way towards high-coherence and scalable multi-qubit devices.
Bingcheng Qing is currently a PhD graduate student at UC Berkeley with Prof. Irfan Siddiqi. He is working on the development of broadband quantum limited amplifier and noise-protected novel qubits, focusing on the single and multi qubit control of Kerr cat qubits with biased noise and their applications in quantum error corrections.